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You can do it with a fixed mount using the natural sidereal motion to drift the sun across the slit as I experimented with here with my LHIRES
http://www.threehillsobservatory.co.uk/astro/spectra_29.htm
With Buil’s other instrument the SolEx, it is essentially a high resolution spectrograph which is mounted on a telescope and the mount is normally driven at x times sidereal, taking advantage of improvements in camera sensitivity and speed to reduce the scan time so the result is less reliant on stable conditions. The details of this device are yet to be revealed thoughSpectrum from 27th Sept
https://britastro.org/specdb/data_graph.php?obs_id=17144
very different from published spectra in quiescence eg
https://skyserver.sdss.org/dr17/en/get/SpecById.ashx?id=8671752135506155520Also picked up by MASTER yesterday at mag 13.6 (clear)
https://www.wis-tns.org/object/2024xhnThere is another PNV from 4 days ago around the same magnitude with no confirmation as yet
http://www.cbat.eps.harvard.edu/unconf/followups/J06393680+1604070.html
https://www.wis-tns.org/object/2024xdmA series of spectra by Peter Velez
https://www.spectro-aras.com/forum/viewtopic.php?t=3150Cheers
RobinThere is an interesting little “Muon Telescope” project here using 4 Geiger detectors in a coincidence detecting array
http://parac.eu/projectmk30.htmCheers
RobinBe interesting if there are spectra from around the same to see what’s happening there
The spectra in the ARAS database
https://aras-database.github.io/database/novavul2024.html
seem to suggest an overall drop in both continuum and H alpha from 20240828-20240907 with H alpha increasing slightly relative to the continuumCheers
RobinIf the spectra are too weak for ISIS to lock on to but overlay each other well in the combined image, you can just leave the fixed Y coordinate position box ticked. (My guiding takes care of the movement in Y so I normally operate this way)
Cheers
RobinIf you try ticking the fixed Y coordinate and sky not removed boxes and rerun the calibration, then click “display image” in the go tab, you will get the sum of your spectrum images with the binning zones overlaid so you can see what is happening. The objective is to have the spectra overlaying each other with the region
with the combined spectrum as narrow as possible. The spectrum binning zone should include all the spectrum region and the sky zones should include none of the spectrum region. If the spectra are not in the same Y position, with the fixed Y coordinate box unticked ISIS will attempt to track the Y movement and overlay them but as David says it may not lock onto faint spectra or with large movements between spectra.Cheers
RobinHi Stan,
The flare and time stamp on the image file name should be correct within a few seconds (2024-08-12 23:27:40 UTC) What time was your fireball ?
The camera takes 10 sec exposures per frame for fainter objects in the deeper sky rather than video for meteors but I am pretty sure what I saw was a satellite, not a fireball.
In the stretched images I can see the faint track for about 50 seconds before the flare, the flare lasted about 20 seconds and the track then continued as before the flare for at least another 10 seconds.
The animation is too big to post here but I have uploaded it to my website here.
http://threehillsobservatory.co.uk/allsky_camera/sat_flare_202408012T23_27_40_stretched.gif
The animation is 20x true speed. Each frame is a 10 second exposure, the yellow arrow marks the track in each image.Did any of the myriad of NEMATODE/GMN cameras in the south of the country pick up your fireball perhaps?
Cheers
RobinWhile testing my new all sky camera last night, some nice displays on the overnight time lapse (sadly not colour though)
http://www.threehillsobservatory.co.uk/allsky_camera/allsky_camera_page.htmCheers
RobinCaught a ridiculously bright satellite glint in the all sky camera last night, straddling two 10 sec exposures. (At first I thought is was a meteor but the faint track can be followed across the sky in the stretched images)
Attachments:
It is probably still useable, with a dab of black paint over the scratch or just avoid putting the spectrum in that region.
Slits wider than the normal seeing are good for extended objects (eg comets nebulae etc) allowing more signal to be collected and for absolute flux measurements ensuring all the flux is collected (both with a reduction in resolution of course)
Cheers
RobinSo how do you handle the blue end with the LHIRES then?
I don’t have a solution so run without a flat, making sure I put the reference star in the same position along the slit and try to include any flat effects in the response. (I don’t use the LHIRES at low resolution and 90% of the time I am working at the red end so it is not a problem there)
I have not investigated it fully but it may be mainly light from the built in lamp leaking round the slit holder. Running a flat lamp ahead of the telescope aperture might be a better solution as the beam will be more tightly controlled. The calibration setup in the LHIRES is rather crude with the lamps just swung in over the slit. The setup in the ALPY calibrator is much better designed.
When selecting the binning region for a spectrum, I stretch the image to make the full top and bottom edges of the spectrum visible. I then set the edge of the spectrum bin to include all of the signal, even the weak parts, while trying not to include any unnecessary background.
Yes this can be particularly important if there is any chromatism or atmospheric dispersion which will change the width of the spectrum along the wavelength axis (or any residual tilt) so the fraction sampled varies. (ISIS has an optimal binning option which seems to cope with this while minimising the sky contribution. It is rather effective on faint targets, though I am not exactly sure how it does it). Similarly the sky background zones need to be set far enough away not to include any of the spectrum. Stretching also helps spot any weak spectra which might be in the selected sky background zones, a bigger problem with slitless setups.
Cheers
RobinCheck for a scratch in the mirror slit coating
If it is that, you should see it in the guider image
Cheers
Robin
